The microporous molecular sieve material has regular pore structures and a large surface area, thus is widely used in the fields of adsorption, separation, chemical engineering, catalysis and the like. In recent years, some new structures of molecular sieve materials have been prepared continuously.
IM-5 molecular sieve is a new zeolite prepared using a bi-quaternary ammonium salt as the templet agent. The IM-5 molecular sieve has a pore-passage structure similar to that of ZSM-5, has a two dimensional 10MR crossing pore structure, and has relatively high thermal stability and hydrothermal stability. Thus the ZSM-5 has a broad prospect of application for catalysis in the petrochemical fields of paraffin cracking, isomerization of n-butylene, preparation of gasoline from Synthesis Gas and the like.
Journal of Molecular Catalysis A: Chemical, 2000, 162: 175-189 Discloses to obtain an IM-5 molecular sieve using 1,1-(pentamethylene)bis-(1-methylpyrrolidinium)bromide as the templet agent, under the condition of adding a promoter of sodium bromide and static hydrothermal conditions at a temperature of 175 degrees C.
Journal of Catalysis 215 (2003) 151-170 discloses to obtain an IM-5 molecular sieve using 1,1-(pentamethylene)bis-(1-methylpyrrolidinium)bromide as the templet agent, under the dynamic hydrothermal condition at a temperature of 160 degrees C.
CN1234012A discloses an IM-5 molecular sieve and the preparation process thereof. The IM-5 molecular sieve is obtained from hydrothermal crystallization at a temperature of 170 degrees C. by adding additional NU-88 powder as a seed crystal.
By studying the products prepared according to the documents above, it can be seen that the IM-5 molecular sieves obtained from prior arts have a morphology of two dimensional rod form with a diameter of generally 50 nm or more and an aspect ratio of generally about 5.
Currently, the preparation of the molecular sieve having a hollow sphere structure is highly interested in the art, in addition to the molecular sieve materials having rod, strip, massive, sphere forms and the like. This is because the special hollow structure may generally cause some special properties of the material, particularly for the catalysis, adsorption, controlled release of medicaments, nano-photoelectricity and the like.
Currently, the hollow sphere of a molecular sieve is prepared predominantly by using a polystyrene microsphere as templet, combining the layer-layer self assembly and a hydrothermal or gas-phase conversion crystallization process. The typically related documents comprise: Chem. Commun., 2000, 2161-2162 and Adv. Mater. 2006, 18, 801-806. This process preparing the molecular sieve hollow sphere using the polymer microsphere as a hard templet has complicated operation steps, poor controllability and relatively high cost.
CN101618336A prepares a MCM-22 molecular sieve hollow sphere by hydrothermal crystallization using carbon black particles as a templet. The carbon black templet has broader sources and lower cost compared with the polystyrene microsphere templet; however, due to the non-uniformity of the carbon black particle as well as a particle size of generally 20 microns or more, the hollow sphere obtained has a relatively large particle size, and correspondingly a thin pore wall, such that the hollow sphere is easy to be broken.
It can be seen that the current preparation with the molecular sieve hollow sphere uses generally a polymer micro sphere and a hard templet such as carbon black and the like, thus the controllability is insufficient. Meanwhile, the amount of the hard templet used is relatively great, which is difficult to be burnt off, and the burn off of the templet may bring abundant environmental pollutants.